The key to Wikipedia’s success is that it gets on with writing an encyclopedia, and doing things that write a good encyclopedia.
Attention paid across the volunteer contributor base to trying to top search engine ranks: somewhere around negligible.
If you focus on giving people really good web pages they want to go to, you’ll get the Google rank Wikipedia has. If you make “SEO” your express goal, rather than actually being, you know, good, you’ll get what you deserve.
(The last occasion I recall anyone at Wikipedia caring about search engine rank was around 2005, when mirror sites of Wikipedia would occupy the first thirty results ahead of the original page; I think someone got in touch with Google and said to them “dude, we should at least rank ahead of our own mirrors.” I presume they decided that automatic sites outranking the human-created originals was silly and did something about that.)